Drag Torque and Synchronization modelling in a Dual Clutch Transmission

Noise, vibration and harshness (NVH) is a big consideration in the automotive industry.
In order to create an as pleasant driving experience as possible for the driver,
NVH should be minimized. One of the sources of NVH comes from the transmission
due to the synchronization process. When shifting between gears, the speeds of the
target gear and the output shaft it is supported by, have to be synchronized. This
is achieved through synchronization rings that, through friction, synchronize the
speeds of the components before engaging them to each other. However, there is a
torque, the gearbox’s drag torque, that can interfere with this process by slowing
down the input shaft. This drag torque therefore aids the synchronization process
during an up-shift and resists it during a down-shift. Today’s automotive industry
lacks a definite method to calculate this drag torque and as a result, values are
assumed to simplify the problem.
This thesis has provided a model that calculates the drag torque at different operating
conditions depending on input speed, input torque, temperature and other
variables. The drag torque comes from several different sources in a transmission and
can be separated into load dependent and speed dependent drag torque. The sources
include viscous shear in the clutch, gears churning in an oil bath, gear windage in an
air-oil mist, bearing rolling elements churning in oil, friction in bearings, friction in
gear meshes, pocketing (also called squeezing) of oil between surfaces in gear meshes
and viscous shear between concentric shafts. The load dependent are those which
are generated through friction, i.e. the friction in bearings and gear meshes. Speed
dependent are those generated through resistance from a surrounding medium.
This thesis has developed multiple models within each source of drag torque and
summed them up for a total drag torque. The results have been compared to test
data to verify which combination of models from each source of drag torque sums up
to a reliable result. The thesis also shows big differences between different models,
but manages to acquire a combination of models that lies relatively close to the test
results.
The thesis has further used the new drag torque model to evaluate the friction lining
on the existing synchronizer rings of a particular transmission to see if the design
is appropriate. It also analyzes how a different inertia in the gearbox influences the
maximum speed the synchronizers are able to synchronize. Here, it is found that
only frictional work and the slip time are influenced of the investigated parameters:
specific frictional work, slip time, pressure, slip speed and specific frictional power.

BibTeX @mastersthesis{Medleri Hire Math2018,author={Medleri Hire Math, Keerthi},title={Drag Torque and Synchronization modelling in a Dual Clutch Transmission},abstract={Noise, vibration and harshness (NVH) is a big consideration in the automotive industry.
In order to create an as pleasant driving experience as possible for the driver,
NVH should be minimized. One of the sources of NVH comes from the transmission
due to the synchronization process. When shifting between gears, the speeds of the
target gear and the output shaft it is supported by, have to be synchronized. This
is achieved through synchronization rings that, through friction, synchronize the
speeds of the components before engaging them to each other. However, there is a
torque, the gearbox’s drag torque, that can interfere with this process by slowing
down the input shaft. This drag torque therefore aids the synchronization process
during an up-shift and resists it during a down-shift. Today’s automotive industry
lacks a definite method to calculate this drag torque and as a result, values are
assumed to simplify the problem.
This thesis has provided a model that calculates the drag torque at different operating
conditions depending on input speed, input torque, temperature and other
variables. The drag torque comes from several different sources in a transmission and
can be separated into load dependent and speed dependent drag torque. The sources
include viscous shear in the clutch, gears churning in an oil bath, gear windage in an
air-oil mist, bearing rolling elements churning in oil, friction in bearings, friction in
gear meshes, pocketing (also called squeezing) of oil between surfaces in gear meshes
and viscous shear between concentric shafts. The load dependent are those which
are generated through friction, i.e. the friction in bearings and gear meshes. Speed
dependent are those generated through resistance from a surrounding medium.
This thesis has developed multiple models within each source of drag torque and
summed them up for a total drag torque. The results have been compared to test
data to verify which combination of models from each source of drag torque sums up
to a reliable result. The thesis also shows big differences between different models,
but manages to acquire a combination of models that lies relatively close to the test
results.
The thesis has further used the new drag torque model to evaluate the friction lining
on the existing synchronizer rings of a particular transmission to see if the design
is appropriate. It also analyzes how a different inertia in the gearbox influences the
maximum speed the synchronizers are able to synchronize. Here, it is found that
only frictional work and the slip time are influenced of the investigated parameters:
specific frictional work, slip time, pressure, slip speed and specific frictional power.},publisher={Institutionen för mekanik och maritima vetenskaper, Chalmers tekniska högskola},year={2018},series={Examensarbete - Institutionen för mekanik och maritima vetenskaper, no: 2018:59},keywords={drag torque, synchronization, dual clutch transmission},}

RefWorks RT GenericSR PrintID 255873A1 Medleri Hire Math, KeerthiT1 Drag Torque and Synchronization modelling in a Dual Clutch TransmissionYR 2018AB Noise, vibration and harshness (NVH) is a big consideration in the automotive industry.
In order to create an as pleasant driving experience as possible for the driver,
NVH should be minimized. One of the sources of NVH comes from the transmission
due to the synchronization process. When shifting between gears, the speeds of the
target gear and the output shaft it is supported by, have to be synchronized. This
is achieved through synchronization rings that, through friction, synchronize the
speeds of the components before engaging them to each other. However, there is a
torque, the gearbox’s drag torque, that can interfere with this process by slowing
down the input shaft. This drag torque therefore aids the synchronization process
during an up-shift and resists it during a down-shift. Today’s automotive industry
lacks a definite method to calculate this drag torque and as a result, values are
assumed to simplify the problem.
This thesis has provided a model that calculates the drag torque at different operating
conditions depending on input speed, input torque, temperature and other
variables. The drag torque comes from several different sources in a transmission and
can be separated into load dependent and speed dependent drag torque. The sources
include viscous shear in the clutch, gears churning in an oil bath, gear windage in an
air-oil mist, bearing rolling elements churning in oil, friction in bearings, friction in
gear meshes, pocketing (also called squeezing) of oil between surfaces in gear meshes
and viscous shear between concentric shafts. The load dependent are those which
are generated through friction, i.e. the friction in bearings and gear meshes. Speed
dependent are those generated through resistance from a surrounding medium.
This thesis has developed multiple models within each source of drag torque and
summed them up for a total drag torque. The results have been compared to test
data to verify which combination of models from each source of drag torque sums up
to a reliable result. The thesis also shows big differences between different models,
but manages to acquire a combination of models that lies relatively close to the test
results.
The thesis has further used the new drag torque model to evaluate the friction lining
on the existing synchronizer rings of a particular transmission to see if the design
is appropriate. It also analyzes how a different inertia in the gearbox influences the
maximum speed the synchronizers are able to synchronize. Here, it is found that
only frictional work and the slip time are influenced of the investigated parameters:
specific frictional work, slip time, pressure, slip speed and specific frictional power.PB Institutionen för mekanik och maritima vetenskaper, Chalmers tekniska högskola,T3 Examensarbete - Institutionen för mekanik och maritima vetenskaper, no: 2018:59LA engOL 30